Telephone system with two-party lines



37111193 1939c H. v. ALEXANDERSEQN m;

TELEPHONE SYSTEM WITH TWO-PARTY LINES Filed Feb 18, 1938 2 Sheets-Sheet 1 fan:

0 s m ma GWEN a H 31 q w m] July 4, 1939 H. v. ALEXANDERSSQN ET AL J Q I TELEPHONE SYSTEM WITH TWO-PARTY LINES Filgd Feb. 18, 1938 2 Sheets-Sheet 2 L 5 Kfl/exan exams on Hu/Zeyifd fizz/anion;

Patented July 4, 1939 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM LINES WITH TWO-PARTY holm, Sweden Application February 18, 1938, Serial No. 191,330 In Sweden November 26, 1936 8 Claims.

The invention relates to telephone systems having two-party lines, i. .e., party lines serving each two subscribers telephones, and particularly to such systems having local battery feed.

In order that systems of the kind referred to shall function satisfactorily, the following requirements must be met.

The calls must be secret while maintaining the possibility of making internal calls. In the i exchange each subscriber should have his own calling equipment, and it should be possible to provide for individual metering of calls, if desired. It should be possible to use ordinary magneto ringers connected by means of two-wire lines to a junction equipment. Through the present invention there has been provided for the first time a system which meets all of said requirements and which, in addition, is simple in operation and can be used also with lines having a comparatively great leakage.

The invention will now be described more in detail with reference to the accompanying drawings, in which Figure 1 shows a first embodiment of the invention, and Figure 2 a second embodiment.

Referring to Figure 1, two subscribers telephones A and B are connected each by means of a two-wire circuit a. or b respectively to a junction equipment comprising two relays A1 and B1 and two condensers C3 and C4. The junction equipment is connected by means of a two-wire junction line La, Lb to the exchange in which individual jacks JA, JB are allotted to the two subscribers A and B.

The relay AI in the junction equipment controls a contact I over which one branch of the circuit a of the subscriber A can be connected to the outgoing line La and also a shifting contact 2 over which the other branch of the circuit a can be connected alternatively to earth and to the branch Lb of the outgoing line. When said branch is connected to earth, a signalling circuit is closed through the subscribers telephone, and a contact 5 controlled by the relay Bl, over the line La to a signalling device SI provided in the exchange, said device being connected at its other terminal to earth. The relay Al also controls a contact 3 which is included in the signalling circuit of the subscriber B. In similar manner the relay BI controls the contacts 4, 5 and 6. Both relays are slow-acting in order not to be actuated by the ringing signals sent out. The line equipment in the exchange consists of two relays A2 and B2, one for each subscriber, two condensers Cl and C2,

and a balancing resistance 9. Said relays are connected in parallel each with a rectifier BA or RB respectively whereby said relays are slowacting, this being necessary in order that the ringing current sent out shall not interfere with the proper operation of the relay. To each subscriber there is also allotted a calling equipment in the form of a drop indicator SI or S2 respectively and a jack JA or JB.

When the subscriber A, by turning his magneto ringer, makes a call the current from the ringer passes from earth over the contact 2, the contact 5, the condenser 03 and the line wire La to earth at the drop indicator Si. When on energization the latter is released a circuit is closed over a contact of the indicator, said circuit extending from the minus pole of the battery and through the relay A2, the line wire La. and the relay Al to earth. The relays Al and A2 are then energized, the relay Al connecting the subscriber A over the contacts I and 2 to the line La, Lb. At the same time the relay AI interrupts at its contact 3 the signalling circuit of the subscriber B, preventing said circuits from making a call. The relay A2 interrupts its contacts 6 and 7, thereby disconnecting the drop indicators SI and S2. The relay A2 also closes a contact 8 thereby connecting a balancing resistance 9, which is earthed at one end, to the line branch Lb over the contact [2. In corresponding manner the relay B2 controls the contacts I!) and H and also the just mentioned contact 12, said contact being opened on operation of the relay B2 thereby preventing the balancing resistance 9 from being connected to any one of the line wires La, Lb while a conversation is being carried on between the two subscribers A and B. The operator thereafter answers the call in ordinary manner by inserting the answering plug into the jack JA. When, after conversation has been finished, the releasing signal indicator drops and the operator takes down the connecting cord, the relays Al and A2 will be deenergized.

A call from the subscriber B is put through in similar manner. The calling signal will then be received at the drop indicator S2.

In case the operator wants to set up a connection to a party line subscriber, for example, the subscriber A, she has only to insert the plug into the jack JA, both relays Al and BI being then energized, whereafter a ringing signal can be transmitted to the subscriber A in ordinary manner.

An internal talking connection, for example,

from the subscriber A to the subscriber B, is set up in ordinary manner with the exception that the operator should take down the answering cord while sending the ringing signal to prevent the subscriber A from hearing the ringing signal, and the telephone of the subscriber A from being connected in shunt to the telephone of the subscriber B.

In the modified embodiment according to Figure 2 the relays Al and BI are each connected in parallel with a rectifier 251 or 23 and connected in series with a winding 2| or 25, each of said windings being connected in parallel with an appertaining rectifier 22 or 24 respectively, said rectifiers being turned in a direction opposite to the direction of the rectifier 20 or 23 respectively. The balancing resistance consists of a winding 26 connected in parallel with a rectiher 21, said winding being connected at one end to the positive pole of a battery the middle point of which is earthed. On a call from, for example, the subscriber A, current will pass from earth in the junction equipment through the rectifier 22 the winding of the relay Al, the line wire La, the relay A2 and to minus pole at the drop indicator Si. At the same time current will pass in the opposite direction over the wire Lb from the plus pole of the battery, through the balancing winding 26, the contact 8 in its upper position, the contact !2, the wire Lb, the rectifier 23 (the latter thus shunting the relay BI) and the winding 25 to earth. After completed talking connection there are thus connected to the wire La the relays Al and A2, and

. to the wire Lb the relay Bi and the balancing winding 26, all of said apparatus being passed by current and all being made as relay windings, wherefore the line becomes very well balanced. The last described connection can therefore be used to advantage in lines in which disturbances occur.

We claim:

1. In a telephone system, a common line, a junction equipment connected to one end of said common line, two subscriber lines branched from said junction equipment, said junction equipment comprising a relay for each subscriber, said relays each being connected at one terminal to an appertaining branch of the common line and at its other terminal to earth, a signalling circuit for each subscriber extending over earth and an appertaining branch of the common line, said junction equipment comprising further for each subscriber one set of contacts, each set consisting of two contacts over which the appertaining subscribers line can be connected to the common line, and a third contact included in the signalling circuit of the subscriber and a fourth contact included in the signalling circuit of the other subscriber, said relays each being adapted to control an appertaining set of contacts.

2. In a telephone system, a common line, connected in one end to an exchange, a junction equipment, connected to the other end of said common line, two subscriber lines. branched from said junction equipment, said junction equipment comprising a relay for each subscriber, said relays each being connected at one terminal to an appertaining branch of the common line and at its other terminal to earth, a signalling circuit for each subscriber extending over earth and an appertaining branch of the commonline, said junction equipment comprising further for each subscriber one set of contacts, each set consisting of two contacts over which the appertaining subscribers line can be connected to the common line, and a third contact included in the signalling circuit of the subscriber and a fourth contact included in the signalling circuit of the other subscriber, said relays each being adapted to control an appertaining set of contacts, and both being further adapted to be energized from the exchange during internal calls.

3. In a telephone system, a common line, a junction equipment connected to one end of said common line, two subscriber lines branched from said junction equipment, said junction equipmentcomprising a slow-acting relay for each subscriber, said relays each being connected at one terminal to an appertaining branch of the common line and: at its other terminal to earth, a signalling circuit for each subscriber extending over earth and an appertaining branch of the common line, said junction equipment comprising further for each subscriber one set of contacts, each set consisting of two contacts over which the appertaining subscribers line can be connected to the common line, and a third contact included in the signalling circuit of the subscriber and a fourth contact included in the signalling circuit of the other subscriber, said relays each being adapted to control an appertaining set of contacts.

4, In a telephone system, a common line, connected in one end to an exchange, a junction equipment, connected to the other end of said common line, two subscriber lines branched from said. junction equipment, said junction equipment comprising a relay for each subscriber, said relays each being connected at one terminal to an appertaining branch of the common line and at its other terminal to earth, a signalling circuit for each subscriber extending over earth and an appertaining branch of the common line, said junction equipment comprising further for each subscriber one set of contacts, each set consisting of two contacts over which the appertaining subscribers line can be connected to the common line, and a third contact included in the signalling circuit of the subscriber and a fourth contact included in the signalling circuit of the other subscriber, said relays each being adapted to control an appertaining set of contacts, a signalling device. for each line branch disposed in said exchange, said device being adapted to be energized when a call is received in the exchange over an appertaining line branch and to close an energizing circuitextending over said line branch to the junction relay connected to said branch.

5. Ina telephone system, a common line connected in one end to an exchange, a junction equipment connected to the other end of said common line, two subscriber lines branched from said junction equipment, said junction equipment comprising a relay for each subscriber, said relays each being connected at one terminal to an appertaining branch of the common line and at its other terminal to earth, and being adapted to be energized from the exchange in a circuit extending over earth and one line branch, a signalling circuit for each subscriber extending over earth and an appertaining branch of the common line, said, junction equipment comprising further for each subscriber one set of contacts, each set consisting of two contacts over which the appertaining subscribers line can be connected-to. the common line; and a third contact included in thesignalling circuit of the subscriber anda fourth contactincluded in the signalling circuit forthe other subscriber, said relays each being adapted to control an appertaining set of contacts, a further relay for each line branch and a balancing resistance earthed at one end which are disposed in said exchange, said energizing circuits for the junction relays each comprising one of said further relay disposed in the exchange, last mentioned relays each being adapted to control a contact by means of which said balancing resistance is connected to the branch of the line to which said last mentioned relay is not connected.

6. In a telephone system, a common line connected in one end to an exchange, a junction equipment connected to the other end of said common line, two subscriber lines branched from said junction equipment, said junction equipment comprising a relay for each subscriber, said relays each being connected at one terminal to an appertaining branch of the common line and at its other terminal to earth, and being adapted to be energized from the exchange in a circuit extending over earth and one line branch, a signalling circuit for each subscriber extending over earth and an appertaining branch of the common line, said junction equipment comprising further for each subscriber one set of contacts, each set consisting of two contacts over which the appertaining subscribers line can be connected to the common line, and a third contact included in the signalling circuit of the subscriber and a fourth contact included in the signalling circuit for the other subscriber, said relays each being adapted to control an appertaining set of contacts, a further relay for each line branch and a balancing resistance earthed at one end which are disposed in said exchange, said energizing circuits for the junction relays each comprising one of said further relay disposed in the exchange, last mentioned relays each being adapted to control a contact by means of which said balancing resistance is connected to the branch of the line to which said last mentioned relay is not connected, one of said further relays also being adapted to control a contact which on internal calls disconnects said balancing resistance.

'7. In a telephone system, a common line connected in one end to an exchange, a junction equipment connected to the other end of said common line, two subscriber lines branched from said junction equipment, said junction equipment comprising a relay for each subscriber, said relays each being connected at one terminal to an appertaining branch of the common line and at its other terminal to earth, and being adapted to be energized from the exchange in a circuit extending over earth and one line branch, a signalling circuit for each subscriber, extending over earth and an appertaining branch of the common line, said junction equipment comprising further for each subscriber one set of contacts, each set consisting of two contacts over which the appertaining subscribers line can be connected to the common line, and a third contact included in the signalling circuit of the subscriber and a fourth contact included in the signalling circuit for the other subscriber, said relays each being adapted to control an appertaining set of contacts, a further relay for each line branch and a balancing resistance earthed at one end which are disposed in the exchange, said further relays being made slow-acting by being connected in parallel each with a rectifier, said energizing circuits for the junction relays each comprising one of said further relay disposed in the exchange, last mentioned relays each being adapted to control a contact by means of which said balancing resistance is connected to the branch of the line to which said last mentioned relay is not connected.

8. In a telephone system, a common line connected in one end to an exchange, a junction equipment connected to the other end of said common line, twosubscriber lines branched from said junction equipment, said junction equipment comprising a relay for each subscriber, said relays each being connected at one terminal to an appertaining branch of the common line and at its other terminal to earth and being connected in parallel with a rectifier and in series, with a winding which is connected in parallel with a rectifier turned in a direction which is opposite to the direction of the first mentioned one, each of said relays being further adapted to be energized from the exchange in a circuit extending over earth and an appertaining line branch, a signalling circuit for each subscriber, extending over earth and an appertaining branch of the common line, said junction equipment comprising further for each subscriber one set of contacts, each set consisting of two contacts over which the appertaining subscribers line can be connected to the common line, and a third contact included in the signalling circuit of the subscriber and a fourth contact included in the signalling circuit for the other subscriber, said relays each being adapted to control an appertaining set of contacts, a further relay for each line branch and a balancing resistance earthed at one end which are disposed in the exchange, said further relays being made slow-acting by being con nected in parallel each with a rectifier, said balancing resistance consisting of a winding which is connected in parallel with the rectifier and is connected at one terminal to the positive pole of a battery the middle point of which is earthed, said energizing circuits for the junction relays comprising each one of said further relay disposed in the exchange, last mentioned relays each being adapted to control a contact by means of which said balancing resistance is connected to the branch of the line to which said last mentioned relay is not connected.

HARALD VALDEMAR ALEXANDERSSO-N. ERIK WALDEMAR HULLEGARD. 

